The present invention relates to file management methods and more particularly, to a file management method which can be effectively used when there are mixedly present, in a single file on a recording medium, data recorded in an operational mode wherein data reliability is essential and data recorded in an operational mode wherein data transmission rate is essential.
A system utilizing a re-writable data recording medium is estimated to have an application as a data storage device of a personal computer (PC) or the like and an application as an audio/video (AV) recorder such as a video recorder or an audio recorder. In the PC application, in general, it is important to secure data reliability; whereas, in the AV application, it is important to secure operation (seamless operation) of recording and reproducing a video or audio signal continuously with respect to time.
In the PC application, in order to secure the data reliability, the data is read immediately after the data is written to determine the presence or absence of a data error. In the presence of a data error, write verify operation is usually carried out for its rewriting. Further, when many times of rewriting operation results in occurrence of the data error, the system determines that its recording area (which will be referred to as the sector, hereinafter) is defective and usually performs replacement processing to replace the sector with another area by its preliminary new recording area (which will be referred to as the replacement sector, hereinafter) previously prepared on the same recording medium. In this case, the system usually combines a plurality of (e.g., 16) sectors each as a minimum recording unit into an error correction code (ECC) block, and performs the replacement processing on a block basis. Similarly, even when reading data, the system performs error judgement. And at the time of error occurrence, the system performs its rereading operation or reads data from its replacement sector. When an uncorrectable data error takes place, it is common practice that the system gives a priority to securing the data reliability and performs its abnormal end operation to stop its writing or reading. Through such operations, the system can minimize the data error which may be inadvertently included and can secure data reliability. However, a data transmission rate (i.e., writing or reading rate) to a recording medium becomes lower. Such write/read operational mode will be referred to as the PC mode, hereinafter.
In the AV application, for the purpose of securing the seamless operation, it is common practice that, even when an error takes place in a data write or read mode, the system ignores the error and continues the writing or reading operation as it is. In this case, the data transmission rate to the recording medium can be kept high but the data reliability is lowered. Such a write/read operational mode will be referred to as the AV mode, hereinafter.
A unit for driving a recording medium generally has previously PC and AV mode recording/reproducing mechanisms, either one of which can be selected by parameter setting of an external control command and then be operated. For example, in the case of a digital versatile disc random access memory (DVD-RAM), the drive unit usually operates in the PC mode. However, when the parameter of a streaming flag bit is set from 0 to 1 and a write or read command is sent to the drive unit, the drive unit can operate in the AV mode.
It is also common to record information indicative of one of which modes wherein the data is recorded on the recording medium together with the data. In the case of the above DVD-RAM, a file system using the subset of the International Standard ISO/IEC1346 is formed on the recording medium, respective data are file-structured for their management, and file type information for identification between a file (which will be referred to as the PC file, hereinafter) recorded in the PC mode and a file (which will be referred to as the AV file, hereinafter) recorded in the AV mode is recorded in management information called a file entry. In this case, a file and the type of the file have a 1:1 relation and thus it is impossible to set a plurality of file types for a single file.
A sector (which will be referred to as the defective sector, hereinafter) containing such a defect as mentioned above includes not only a sector containing a physical defect on a recording medium but also a sector from which data cannot be normally read or written due to a deposition of dust or fingerprint thereon.